For fugitive dust emissions control, petroleum coke calciners use a variety of petroleum-derived dust suppression agents. These agents are commonly selected from a broad range of distillation fractions from crude oil processing. Agents may be selected from vacuum tower bottoms to asphalt to lube oils to paraffin wax, and these agents may possibly be mixtures formed from various combinations of distillate cuts.
The choice of dust suppression agent on petroleum coke has not been a concern of carbochlorination manufacturers beyond, perhaps, the hydrogen content of the agent and the weight percent loading of agent on the coke. Hydrogen content of the agent impacts the amount of hydrochloric acid that must be separated and removed from the carbochlorination products, particularly in the case of metal chloride product(s). Selection of suitable agents for use in the field of carbochlorination, as in other manufacturing processes has primarily been based on low cost.
Petroleum coke calciners here-to-fore have had essentially two criteria for dust suppressants: 1) flash point and 2) viscosity. A relatively high flash point is important from a safety perspective because suppression agents are typically applied to hot petroleum coke as the coke exits the after-cooler downstream of the calciner. Viscosity is important because it is indicative of tackiness for dust capture and retention. The dust-control efficacy of petroleum-derived dust suppression agents is somewhat dependent on viscosity. Another desirable property is a low pour point to avoid the need for the heat tracing of vessels and piping that store and deliver the suppression agent to the petroleum coke.
The inventors of the present invention have discovered that the certain petroleum-derived dust suppression agent impact, at trace levels, the production of halogenated organic PBT""s (persistent, bio-accumulative, and toxic pollutants) in carbochlorination processes, specifically titani-ferrous ore carbochlorination. The selection of dust suppression agents according to the present invention lowers the production of trace quantities of halogenated organic PBT""s.
The present invention provides a composition and a method for reducing the production of persistent bio-accumulative and toxic pollutants in solid carbonaceous reduction reactions in the carbochlorination processes.
The composition of the invention comprises composition for reducing production of persistent, bio-accumulative, and toxic haloginated pollutants in carbochlorination processes comprising a solid carbonaceous reductant and a predominately linear- and branched-chain saturated hydrocarbon having low color, a viscosity in the range of 500 to 800 SUS at 100 degrees F. and a flash point above 450 degrees F. wherein the concentration of the hydrocarbon on surface of the reductant is the minimum concentration of the hydrocarbon necessary to control fugitive dust emissions.
The method of the present invention comprises using the composition of the present invention in carbochlorination. Examples of carbochorination processes are processes for the production of metals from their chlorides such as titanium, aluminum and zirconium chlorides for the production of the respective metals or the oxides. The reductant in these reactions is a source of solid carbon particles called herein a solid carbonaceous reductant. The most common solid carbonaceous reductant used in these reactions is petroleum coke although other cokes and carbon sources are suitable for use.